This proposal concerns the continuing investigation of the psychological, clinical, and psychophysical factors that affect pain due to electric shock: a) Psychological Factors - Investigate the effect of control and predictability on the perception of the intensity of electrical stimulation and evaluate the role of distraction in the process; b) Clinical Factors - Replicate and extend previous work dealing with the applicability of the Melzack-Wall spinal gating concept in altering the subjective judgments of pain intensity and examine alternative procedures of maximizing large fiber discharge. Test whether the sensory and reactive components of the pain experience produced by electric shock are differentially affected by clinical (ischemic) pain. c) Psychophysical Factors - Investigate whether differences in intensity and duration of the shock stimulus alter evaluation of discomfort, pain, and tolerance judgments.